Please answer i have a test in 11 hours

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Discussion Overview

The discussion revolves around the behavior of brightness in a parallel circuit when additional bulbs and resistors are introduced. Participants explore the relationship between voltage, current, power, and brightness in the context of electrical circuits, particularly focusing on how these factors interact when components are added.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asserts that in a parallel circuit, brightness remains constant as voltage across each bulb is equal to the battery voltage, even when more bulbs are added.
  • Another participant questions the impact of adding resistors, suggesting that lowering the equivalent resistance (REQ) could lead to a drop in current, which might reduce power and thus brightness.
  • A different participant clarifies that if resistors are added in series with each bulb, it would limit current and reduce voltage across the bulbs, potentially decreasing brightness.
  • One participant emphasizes that adding resistors in parallel reduces equivalent resistance but increases total current from the battery, maintaining the same current through each bulb.
  • Another participant notes that while brightness might decrease due to the battery being under load, this is contingent on the ratings of the bulbs and the battery parameters.

Areas of Agreement / Disagreement

Participants express differing views on how adding resistors affects current and brightness in parallel circuits. There is no consensus on the implications of adding resistors, and the discussion remains unresolved regarding the impact on brightness.

Contextual Notes

Participants reference various assumptions about circuit configurations, such as whether resistors are added in series or parallel, and the specific ratings of bulbs and battery, which may influence the outcomes discussed.

syracuseking96
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In a parallel circuit, I know that the brightness stays the same even if you add more bulbs because the voltage is the same as the battery's in each bulb. But, if when you add resistors the REQ is lowered, doesn't that mean the current drops? And if the current drops and the voltage stays the same, wouldn't that make the power lower. Since power is what determines brightness, how can the brightness stay the same?
 
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where are you adding the resistors ?
in series with each bulb ?

if so, then you will get current limiting through each resistor, and IF the resistors are all the same value
then you will get the same amount of voltage drop across each resistor.
So then each globe in series with its resistor will see a lower but the same voltage.
the resistor value will determine the voltage drop and therefore the brightness of each globe which will of course not be as bright as when supplied with the original voltage

say the original voltage is 12V and the globe is a 12V rated globe, but the resistor value drops the voltage to 6V, that means the globe is now only getting 6V across it and I would expect it to be ~ 1/2 the brightness

Dave
 
NOOO... I am adding more bulbs in parallel. It is the most basic parallel circuit.
 
syracuseking96 said:
In a parallel circuit, I know that the brightness stays the same even if you add more bulbs because the voltage is the same as the battery's in each bulb. But, if when you add resistors the REQ is lowered, doesn't that mean the current drops? And if the current drops and the voltage stays the same, wouldn't that make the power lower. Since power is what determines brightness, how can the brightness stay the same?

syracuseking96 said:
NOOO... I am adding more bulbs in parallel. It is the most basic parallel circuit.

You misunderstand Dave's helpful post. He is assuming you are asking about putting each bulb+resistor segment in parallel.
 
syracuseking96 said:
In a parallel circuit, I know that the brightness stays the same even if you add more bulbs because the voltage is the same as the battery's in each bulb.

Correct.

But, if when you add resistors the REQ is lowered, doesn't that mean the current drops?

No. Adding resistors in parallel does reduce the equivalent resistance of a circuit but it increases the total current from the battery. However the current through each resistor stays the same.

Same voltage & same current in each bulb (or resistor) = same power in each bulb (or resistor).
 
Yes indeed in a parallel circuit current stays the same through each element.

Although the brightness might decrease in parallel circuit because of the battery being under load but that depends on the rating of the bulbs you have put in the circuit and the battery parameters.
 

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